How do electric organs form in mormyrid and gymnarchid fishes?

In mormyrid and gymnarchid fishes, electric organs are formed through the modification of a short length of body musculature located toward the tail.1

During this process, the muscle cells lose their ability to contract and undergo significant cellular reorganization. They transform from slender, ordinary muscle fibers into thin, flattened structures known as electroplaques, which are the specialized cells responsible for producing electricity.12

The number of these electroplaques varies by group, with mormyrids typically possessing about 300 to 400, while Gymnarchus (the sole genus of the Gymnarchidae) contains approximately 600 to 800. This evolutionary adaptation allows these fishes to generate electrical pulses used for navigation, detection, and signaling in their environment.13